Background: Quality assessment of children's functioning is critical for both research and service delivery. The Strengths and Difficulties Questionnaire (SDQ) is a brief, publicly-available instrument that provides such assessment. Although the SDQ has strong psychometric properties, less is known about its responsiveness or sensitivity to detecting change over time. Objective: This study examined the responsiveness of the SDQ among high-risk youth and tested the degree to which changes on the SDQ correspond to changes on the Child Behavior Checklist (CBCL), a well-established and lengthier reference measure. Methods: Longitudinal SDQ and CBCL data collected as part of routine service delivery were analyzed for 65 youth entering a large residential treatment program. Assessments were obtained both at intake and approximately 3 months into the program. Results: Paired samples t tests revealed statistically significant decreases in SDQ Conduct Problems and Emotional Symptoms scores, and McNemar's tests showed a statistically significant decrease in the proportion of Conduct Problems cases. Correlations between changes on the SDQ scales and changes on corresponding CBCL scales ranged from 0.58 to 0.83. Results from receiver operating characteristic curves indicated that the SDQ was relatively accurate in identifying changes in CBCL diagnostic cases, with overlap across corresponding problem behavior domains ranging from 68 to 81%. Conclusions: Findings suggest that the SDQ may represent a shorter, low cost alternative to longer measures, such as the CBCL, for use when researchers and practitioners are faced with time or financial constraints associated with the assessment of child functioning over time.